1. Field of the Invention:
This invention relates to an anti-skid control system for a motor vehicle of the type that the drive system thereof is switchable between two-wheel drive (referred to as 2WD hereinafter) and four-wheel drive (referred to as 4WD), and more particularly it pertains to such an anti-skid control system which is designed such that when the drive system of the motor vehicle is switched from 2WD to 4WD or vice versa, the anti-skid control is changed to be suitable for the type of the switched drive system.
2. Description of the Prior Art:
An anti-skid control system for a motor vehicle of the 2WD type such as, for example, the front-engine, front-drive type (referred to as FF type hereinafter) is usually of the three-channel type wherein the front wheels of the motor vehicle are controlled independently of each other while the rear wheels thereof are controlled on the basis of the lower one of the rear wheel velocities (referred to as "select low" hereinafter), so that the front wheels are permitted to rotate at normal speeds, while the rear wheels are intermittently braked and relieved. In the case where such a system is employed with a motor vehicle of the type that the drive system is switchable between 2WD and 4WD, however, when the drive system is changed from 2WD to 4WD, speed differences tend to occur between the front and rear axles of the motor vehicle because of the fact that all the wheels are coupled directly to each other during 4WD operation, so that due to such speed differences, the wheels are caused to interfere with each other; thus, the result is such that the anti-skid control system is prevented from working properly so that "jerky feeling" is produced and in a worse case the motor vehicle is caused to swerve so that the directional stability thereof is deteriorated.